Most of the 'smart' chargers ain't too smart at times, so I've piggy-backed another 'good' battery to trick them too. I also have a brute charger for when the smart-ass chargers refuse and I don't care to lift a battery out of one of the other vehicles. I keep a Deltran 'Battery Tender'® connected to the Harley the entire time it's parked in the garage.
Word of caution - some auto manufacturers recommend disconnecting one of the battery cables before charging your battery. Yes, you might loose your radio presets, and if you have an impending smog test, you may loose ECU history data, which may cause a normally good clean running vehicle from passing said smog test.
Some vehicles need to be driven up to 300 miles for the ECU to clear error codes, or provide adequate data to the smog test computer. It happened with my Tacoma last year, but luckily, only took about 60 miles to clear the code(s) ... and passed the smog
re-test just fine (for an additional $ amount)